/Engine/Source/Runtime/Engine/Classes/Components/AudioComponent.h
Sets how much audio the sound should send to the given Audio Bus (PRE Source Effects). if the Bus Send doesn't already exist, it will be added to the overrides on the active sound.
void SetAudioBusSendPreEffect ( [UAudioBus](API\Runtime\Engine\Sound\UAudioBus) * AudioBus, float AudioBusSendLevel )